Camera stand head

ABSTRACT

The invention relates to a camera stand head comprising a device ( 17, 18, 19, 20 ) for attenuating a tilting movement, and a device for compensating gravity torque occurring during the tilting movement. The device for compensating the gravity torque comprises at least one first, fixed bearing ( 4 ), at least one second bearing ( 5 ) which is connected to an inclinable part, and at least one torsion spring ( 7 ) having adjustable torsion rigidity. Said torsion spring is arranged between the bearings ( 4, 5 ) and comprises at least one spring bar ( 8 ), the axis of the spring bar being spatially offset in relation to the central axis ( 15 ) of the torsion spring ( 7 ). The characteristic curve (torque over angle of rotation) of the torsion spring extends essentially in a sinusoidal manner.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a camera stand head comprising a devicefor attenuating a tilting movement, and a device for compensatinggravity torque occurring during this tilting movement.

Cameras which cannot be hand-held, for example owing to their weight orsize or owing to specific requirements of a smooth camera movement, arerested on a camera stand or a camera pedestal. The camera is thereforemounted on a camera stand head so as to be rotatable about a horizontalaxis (tilting axis) and a vertical axis (swivel axis) so that thecameraman can follow moving objects with the camera lens. (In thefollowing, only the expression “camera stand” is used; the statementsare, however, also valid for camera pedestals). When tilting the camera,i.e. when rotating the camera stand head about its tilting axis, thedistance of the centre of gravity of the camera from this tilting axis(height of the centre of gravity) together with the weight of the cameracauses a torque about the tilting axis, which is dependent on thetilting angle.

The weight compensation device is supposed to allow a force-free tiltingof the camera by compensating this tilting torque. It is thus necessaryfor the weight compensation to be quickly and easily adaptable todifferent weights and different heights of the centre of gravity owingto the rapid change of the load torque when putting on different camerasor camera accessories such as teleprompters etc.

Furthermore, the weight compensation is supposed to hold the cameradirectly in any tilting position without any subsequent movement, andthis within a tilting range of at least ±90°, in order to be able tocover the entire spatial field of vision when tilting the camera.

To allow gentle tilting movements, the camera stand head shouldfurthermore comprise an attenuating device which is independent ofweight compensation and is preferably also adjustable.

2. Prior Art

Known camera stand heads comprise, for example, a hydraulic attenuatorhaving an adjustable torsional resistance to attenuate the tiltingmovement, as is described in the German patent specification 24 57 267.

Regarding weight compensation, it is known, for example, to compensatethe tilting torque with several disk torsion springs made of rubber andarranged consecutively on the tilting axis. Weight compensation can beadapted here by the connection or disconnection of individual springs.It is furthermore known to compensate the tilting torque by means ofseries connected pressure or tension springs.

If the centre of gravity of the camera lies exactly vertically over thetilting axis at a tilting angle of 0°, the tilting torque has asinusoidal characteristic curve. The characteristic curve (torque overangle of rotation) of the known arrangement of disk torsion springs is,however, approximately linear so that although it roughly concurs withthe sinusoidal characteristic curve of the tilting torque in a tiltingrange of 0° to approximately 45°, it does, however, deviate increasinglyfrom this characteristic curve at tilting angles of >45°. Thecompensation torque is therefore too great at large tilting angles andthus a subsequent reverse movement of the camera occurs in the directionof the compensation position.

SUMMARY OF THE INVENTION

The object of the present invention is thus to create a camera standhead having a device for attenuating a tilting movement and a device forcompensating gravity torque occurring during this tilting movement,which compensates the tilting torque more accurately.

This object is solved according to the invention by means of a camerastand head having the features herein.

Therefore, the device for compensating gravity torque comprises at leastone first, fixed bearing, at least one second bearing connected to aninclinable part and at least one torsion spring arranged between thesebearings, said torsion spring having adjustable torsion rigidity andcomprising at least one spring bar, the axis of said spring bar beingspatially offset in relation to the central axis of the torsion spring,with the characteristic curve (torque over angle of rotation) of thetorsion spring extending essentially in a sinusoidal manner.

The sinusoidal characteristic curve of the torsion spring is formed onthe basis of the arrangement of the spring bar or spring bars parallelto the axis of the torsion spring. When twisting the entire torsionspring, the spring bars are deflected, with the type of stress of thespring bars (bending and possibly torsion) and thus also deflectionbeing dependant on how the spring bars are arranged in the two bearingsof the torsion spring. The different possibilities of fixing will bediscussed below. In any case, the spring rigidity of the torsion springof the camera stand head according to the invention is adapted to theweight of the camera which is currently located on the camera stand headand then has characteristics which correspond exactly to thecharacteristics of the gravity torque of the camera when tilting aboutthe tilting axis: when the centre of mass of the camera lies exactlyvertically above the tilting axis, no torque is created by the torsionspring. When the camera is tilted from the resting position, the tiltingtorque caused by the weight of the camera increases in a sinusoidalmanner as the tilting angle increases and the compensation torquegenerated by the torsion spring also simultaneously increases in asinusoidal manner. The tilting torque will thus be compensated by anequally large counter-torque at any tilting angle so that the cameraremains balanced in any tilting position. The cameraman then onlyrequires minimal strength to tilt the camera and the camera remains atany tilting angle.

The curve of the compensation torque corresponds to the curve of thetilting torque when tilting the camera in the entire tilting range of atleast +90° so that the camera can be tilted at large angles with just aslittle strength as at small angles and that also at large angles, thecamera remains in any desired position without subsequent movement.

In an advantageous design of the camera stand head according to theinvention, the torsion rigidity of the torsion spring can be smoothlyadjusted. The spring rigidity can thus be precisely adapted to camerashaving any weight and any height of the centre of gravity, with commoncameras, including accessories, having a weight of up to 150 kg and aheight of the centre of gravity of up to 50 cm. In the case ofteleprompters and other camera accessories which can also be mounted onthe camera stand head according to the invention, there may be weightand leverage ratios which differ therefrom; the gravity torque caused bysuch superstructures can also be compensated by the weight compensationdevice according to the invention.

There are various possibilities for adjusting the torsion springrigidity. In a first advantageous design of the invention, the secondbearing of the weight compensation device connected to the inclinablepart is axially shiftable in relation to the fixed bearing andfurthermore comprises a coulisse in which the bar ends of the springbars can slide. When shifting the second bearing relative to the firstbearing, the ends of the bars slide in the coulisse of the secondbearing, whereby the spring bars are subjected to bending stress and arethus deflected and pre-stressed. This deflection changes the effectivelever of the spring bars during the torsional movement of the entiretorsion spring, and thus changes the torsion spring rigidity, with thecurve of the compensation torque, however, being constantly sinusoidal.

In order to adjust the torsion spring rigidity, an adjusting device canalternatively or additionally be provided, which is arranged between thetwo bearings of the torsion spring and is shiftable along the axis ofthe spring bars. The adjusting device is thus preferably formed in sucha way that it changes the effective length of the spring bars so thatthey are only resiliently deformed in a partial area rather than acrosstheir entire length when the torsion spring is twisted. A dynamicinfluence of the effective spring length is then also possible, wherebythe characteristic curve of the torsion spring can be adapted tospecific requirements.

The spring bars can generally only be fixed in the first bearing or inthe first and second bearing. When the torsion spring is twisted, thestress of the spring bars changes depending on the fixing thereof: ifthe spring bars are free at one end, they will only be subjected tobending stress and if they are fixed at both ends, they will besubjected to both bending and torsional stress. This different stressaffects the curve of the compensation torque and can thus be used tooptimise this curve.

There are also several possibilities with regard to the design of theindividual spring bars. An individual spring bar can thus be designed,for example, as a cylindrical bar, a slitted tube, a square bar or as aconical bar. A slightly changed characteristic curve of the spring willoccur depending on the design of the spring bar. Instead of a singlespring bar, a bundle of spring bars can also be used, the deflectionstate of which will differ from the deflection state of an individualspring bar during twisting. Thus, the characteristic curve of the springcan be influenced and adapted to the respective ratios.

Finally, to further change and optimise the shape of the characteristiccurve, an attenuating insert or coating of the spring elements can, forexample, be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiment examples of the invention are described in more detail belowwith regard to the enclosed drawings.

FIG. 1 shows a schematic view of a camera stand,

FIG. 2 shows a weight compensation device for a camera stand headaccording to the first embodiment of the invention,

FIG. 3 shows a torque characteristic curve (torque over angle ofrotation) of a camera stand head according to the invention,

FIGS. 4 and 5 show a schematic view of a second embodiment of a camerastand head according to the invention,

FIG. 6 shows a sectional view along the line A—A in FIG. 5, and

FIG. 7 shows a detailed view of section Z in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 schematically shows a camera stand 1 having a camera stand head 2as well as a camera 3 mounted thereon. The camera has been moved aboutthe tilting angle φ with regard to its balanced position, in which thecentre of gravity S thereof is located exactly vertically over thetilting axis N running traverse to the drawing plane. Owing to thedistance a of the centre of gravity of the camera from the tilting axisN, a lever arm b=a sin φ is formed which, together with the weight Fs ofthe camera, causes a tilting torque M about the tilting axis N. As theangle φ increases, the tilting torque M=Fs a sin φ increases in asinusoidal manner.

FIG. 2 shows a device for compensating this tilting torque whichincreases in a sinusoidal manner. The device comprises a torsion spring7, a first, fixed bearing 4 as well as a second bearing 5 which isconnected with the inclinable part of the camera stand. The secondbearing 5 is configured in a conical manner and comprises grooves 6, theaxes of which intersect the main axis of the torsion spring 7.

The grooves extend straightly in the embodiment example; however, thegrooves could also be designed in a curved manner in order to allow thecharacteristic curve of the torsion spring to extend according tospecific requirements. The axes of the grooves can furthermore extendskew to the main axis of the torsion spring.

The torsion spring comprises a series of spring bars 8 which areprovided with ball-shaped end pieces 9 at one end, which are slideablyarranged in the grooves 6 of the second bearing 5. The opposite ends 10of the spring bars are arranged in the first bearing 4 in such a waythat they are not prevented from rotating about their own axis and arefurthermore axially shiftable.

When tilting the camera, the second bearing. 5, which is connected withthe inclinable part of the camera stand, is thus twisted relative to thefirst bearing 4 so that the torsion spring 7 is twisted. If the ends 9of the spring bars are not fixed in the second bearing 5, rather areable to rotate about their own axis in this bearing, they are onlysubjected to bending stress when the entire system is twisted. If thespring bars were prevented from rotating about their own axis in bothbearings 4 and 5, they would additionally be subjected to a torsionalstress. The characteristic curve of the torsion spring has thesinusoidal curve shown in FIG. 3.

The second bearing 5 can be smoothly shifted along the main axis of thetorsion spring 7. When shifting the second bearing 5 in the direction ofthe first bearing 4 in FIG. 2, the ball ends 9 of the spring bars 8slide in the grooves 6 of the second bearing 5. Owing to the conicalshape of the second bearing 5, the spring bars 8 are bent when doing so,i.e. the ball ends of the spring bars are spread apart. Therefore, ifthe second bearing 5 is twisted in the axially shifted state relative tothe first bearing 4, a characterising curve deviating from thenon-shifted state occurs. FIG. 3 clarifies this difference: if thesecond bearing is not axially shifted, i.e. if the spring bars are notspread apart, a flatter characterising curve A occurs. If the secondbearing is axially shifted to the maximum in the direction of the firstbearing, a steeper characterising curve B occurs so that correspondinglylarger gravity torques of a heavier camera can be compensated. Withinthe adjustment range labelled as 12 in FIG. 3, any sinusoidalcharacterising curves can be formed by adjusting the torsion springrigidity. A change in the spatial extension of the grooves in grooves inthe moveable bearing can also cause a change in the characterisingcurve.

The axial shifting of the second bearing in the direction of the firstbearing can be carried out by means of a simple adjusting lever 11 onthe camera stand head, which furthermore enables the second bearing tobe stopped in any axial position. The torsion spring rigidity can thusbe quickly, easily and precisely adapted to different camera weights orother changes in weight.

FIGS. 4 and 5 show a second embodiment example of the camera stand headaccording to the invention. The spring bars 8 are fixed at one end in afirst bearing 4 and are mounted at their other end by means of rolls 13which are intended in this embodiment to adjust the effective springlength. These rolls are connected with the torsion axis 15 via carriers14 and thus with a second bearing 5 which is in turn connected with theinclinable part of the camera stand head. When the second bearing 5 istwisted relative to the first bearing 4, the twisting movement isaccordingly transferred to the spring bars 8 via the torsion axis 15,the carriers 14 and the rolls 13. The rolls 13 are thereforeindividually shiftable along the axis of the respective spring bars.Since the rolls 13 in the state represented in FIG. 5 are shiftedfurther in the direction of the second bearing 5 than those in FIG. 4,the effective spring length of the spring bars 8 represented in FIG. 5is correspondingly longer than that of the spring bars 8 represented inFIG. 4. The device for attenuating the tilting movement can also be seenfrom FIG. 4. Annular discs 17 and distancing tubes 18 are alternatelyarranged on a shaft 16 whose torsion movement is to be attenuated. Anintermediary disc 19 is assigned to each annular disc 17.

An attenuating liquid is located between the annular discs 17 and theintermediary discs 19. The intermediary discs 19 are engaged at theirouter periphery with a coupling element 20. This coupling element 20allows any number of intermediary discs 19 and annular discs 17 to belocked relative to the casing, i.e. to be prevented from turning. Ahydraulic attenuating force occurs owing to the relative movement of theannular discs 17, with it being possible to adjust the degree ofattenuation of the device by means of the number of annular discs 17 andintermediary discs 19 which are locked relative to the casing.

FIG. 6 is a sectional view along the line A—A in FIG. 5, in which thearrangement of the rolls 13 and the spring bars 8 is clearly shownagain. It can be seen in particular from the detailed view in FIG. 7that bundles of spring bars 8 are used in this embodiment.

1. A camera stand head having a device (17, 18, 19, 20) for attenuatinga tilting movement and a device for compensating gravity torqueoccurring during the tilting movement, characterised in that the devicefor compensating gravity torque comprises at least one first fixedbearing (4), at least one second bearing (5) connected with aninclinable part as well as at least one torsion spring (7) arrangedbetween said bearings (4, 5), said torsion spring having adjustabletorsion rigidity and comprising at least one spring bar (8), the axis ofsaid spring bar being spatially offset in relation to the central axis(15) of the torsion spring (7), with the characteristic curve (torqueover angle of rotation) of the torsion spring (7) extending essentiallyin a sinusoidal manner.
 2. A camera stand head according to claim 1,characterised in that the torsion rigidity of the torsion spring (7) canbe smoothly and continuously adjusted.
 3. A camera stand head accordingto claim 2, wherein the torsion rigidity of the torsion spring (7) isadjustable by axially shifting at least one bearing (4, 5).
 4. A camerastand head according to claim 1, wherein the torsion rigidity of thetorsion spring (7) is adjustable by axially shifting at least onebearing (4, 5).
 5. A camera stand head according to claim 1, wherein thedevice for compensating gravity torque comprises an adjusting device foradjusting the torsion spring rigidity of the torsion spring, which isarranged between the first (4) and second (5) bearings to be shiftablealong the axis of the spring bars (8).
 6. The camera stand headaccording to claim 1, wherein the spring bars (8) are fixed in an axialdirection in a bearing (4, 5) at at least one end (9, 10) of the bar. 7.A camera stand head according to claim 1, wherein the spring bars (8)are fixed at at least one end (9, 10) of the bar in a bearing (4, 5) insuch a way that they are prevented from rotating about their own axis atthis end (9, 10) of the bar.
 8. A camera stand head according to claim1, wherein the spring bars (8) are shiftably mounted in a bearing (4, 5)at at least one end (9, 10) of the bar.
 9. A camera stand head accordingto claim 8, characterised in that the spring bars (8) are mounted in abearing (4, 5) at at least one end (9, 10) of the bar so as to beshiftable along an axis which intersects the main axis (15) of thetorsion spring (7).
 10. A camera stand head according to claim 8,characterised in that the spring ends (8) are mounted in a bearing (4,5) at at least one end (9, 10) of the bar so as to be shiftable along anaxis which lies skew to the main axis (15) of the torsion spring (7).11. A camera stand head according to claim 8, characterised in that thespring bars (8) are mounted in a bearing (4, 5) at at least one end (9,10) of the bar so as to be shiftable along an axis which lies parallelto the main axis (15) of the torsion spring (7).
 12. A camera stand headaccording to claim 8, wherein the ends (9, 10) of the bars move alongthe axis in a straight line when shifted.
 13. A camera stand headaccording to claim 8, wherein the ends (9, 10) of the bars move alongthe axis in a curved line when shifted.
 14. A camera stand headaccording to claim 1, wherein the spring bars (8) are rotatably mountedin a bearing (4, 5) at at least one end (9, 10) of the bar.
 15. A camerastand head according to claim 1, wherein the spring bars (8) areprovided with the ball-shaped end pieces at at least one end (9, 10) ofthe bar and at least one bearing (4, 5) comprises grooves into which theball-shaped end pieces engage.
 16. A camera stand head according toclaim 1, wherein the spring bars (8) are mounted in a bearing (4, 5) atat least one end (9, 10) of the bars by means of rolls (13).
 17. Acamera stand head according to claim 1, wherein several spring bars (8)arranged at regular intervals across the circumference of the torsionsprings (7) are provided.
 18. A camera stand head according to claim 1,wherein the camera stand head comprises several torsion springs (7)arranged to be connected in series or in parallel or are stacked.
 19. Acamera stand head according to claim 1, wherein the spring bars (8) areconfigured as cylindrical bars, slitted tubes, square bars or as conicalbars.
 20. A camera stand head according to claim 1, wherein the torsionspring (7) comprises at least one bundle of spring bars (8) instead ofat least one individual spring bar (8).